This research examines the interactions of insulin-like growth factor-1 (IGF-1) with growth hormone, amino acids, and insulin on human skeletal muscle protein metabolism. After baseline measurements, IGF-1 will be infused intraarterially and GH or amino acids added systemically. In a separate study, insulin will be co-infused with IGF-1. Repeat measurements will be made after 3 and 6 hours of infusions. These studies have demonstrated both the vascular and metabolic effects of IGF-1 infused intra-arterially in healthy control subjects. IGF-1 markedly stimulates forearm blood flow, skeletal muscle glucose uptake, and protein anabolism. Most recently, we have noted that the effect of IGF-1 is gender specific.